The invention relates to a fuel tank for a motor vehicle, having a reservoir arranged therein and being accessible through a closable opening in the wall of the fuel tank.
Particularly in the case of the one-piece fuel tanks of thermoplastic material, which are usual nowadays, the size of the reservoir, which generally also contains the fuel pump for supplying the engine, is subject to certain limitations. This is to be attributed to the fact that the reservoir is either subsequently inserted into the fuel tank through an opening in the wall thereof, or it is already inserted during the production procedure into the preform from which the fuel tank is formed. In the former case the dimensions of the opening in the wall of the tank, which cannot be selected to be just any dimensions, determine the size and thus the capacity of the reservoir. The latter situation involves restrictions in regard to the size of the reservoir, which arise out of reasons relating to production procedures and in particular also out of the cross-sectional dimensions of the preform, which is generally produced by means of extrusion and which is expanded to form the tank by virtue of an internal increased pressure in a blow molding mold.
On the other hand, extreme operating states of the motor vehicle, for example due to an extreme position of inclination or very high levels of centrifugal force when negotiating bends, can have the result that a possibly large amount of fuel is drawn per unit of time exclusively from the reservoir, in which case it is necessary to ensure that, even under those conditions, there is always a sufficient amount of liquid within the reservoir in the proximity of the intake opening of the fuel pump.
In many cases, therefore, it is deemed necessary for the reservoir to involve a filling volume of at least two liters so that, for example in the case of off-road vehicles, a sufficiently large amount of fuel can be held in the intake region of the fuel pump over a prolonged period of time under all operating conditions which come into consideration in a practical context. In that respect, it is to be borne in mind that, under certain operating conditions, for example when the vehicle is in an inclined position, there is a tendency for the fuel to flow into the region of the reservoir which is lowest in the respective inclined position and to collect there so that, even when the tank has a relatively large reservoir, under some circumstances there is no longer any fuel in the intake region of the fuel pump.
Accordingly, an object of the present invention is to design a fuel tank of the type described at the outset of this specification so that, even if the interior of the tank involves only restricted accessibility, it is possible to provide a reservoir which is sufficiently large as to ensure the presence of a sufficiently large amount of fuel in the reservoir in the intake region of the pump under all travel conditions which come under consideration in practical operation.
The way in which this object is attained can be summarized to the effect that the reservoir comprises at least two modules which can be connected together and which are assembled within the tank to form the reservoir, wherein all modules can be inserted into the tank through the opening in the tank wall. However, it is also possible that in production of the tank at least one module is already inserted therein, and additional modules, after production of the tank and possibly also after the provision of a special opening in the tank wall, are inserted into the tank and connected to each other and/or to the module already disposed in the tank.
The resulting reservoir will generally be too large for it to be capable of being introduced into the tank through the opening in the wall of the tank. Therefore, it will generally be dependent on so selecting the size of the individual modules and the shape thereof that, on the one hand, they can be inserted through the opening in the wall of the finished tank into the tank or into the preform from which the tank is produced, and all modules can then be connected in the tank to each other and to the wall of the tank. In this regard, there is no need for the modules to be connected together in the position of the reservoir which corresponds to the operating position of the reservoir.
In addition, in particular, depending on the size of the individual modules, it may be desirable to provide them with internal fitments or baffles in order to ensure that, when negotiating prolonged bends or when the vehicle is in an inclined position, the fuel does not collect in a short time, for example in the lowermost region of the respective module. A labyrinth-like geometry is normally provided in any case in the module which accommodates the fuel pump, by virtue of the pump and the associated components, and that geometry prevents this module from running empty in a very short period of time under the abovementioned operating conditions.
Filling of the modules can be effected by way of a fuel pump, which can be of a two-stage nature, wherein the first stage serves for filling the reservoir and the second stage supplies the engine with fuel from the reservoir. However, it is also possible to provide a single-stage motor-driven pump and at least one suction jet pump, by means of which the reservoir is filled. The latter, that is to say the modules forming it, are advantageously sealed off in such a way that, when the pump or pumps is or are stopped, as far as possible no fuel flows out of the reservoir into the space surrounding it in the tank.
It may also be desirable for at least a part of the modules to be closed on the top side except for a small orifice, in order thereby to prevent fuel from sloshing in relatively large amounts out of the respective module at the top.
It is also possible for different functions to be associated with the modules in such a way that, for example, at least one module is in the form of a fuel filter or is provided with such a filter. There is also the possibility of associating with at least one of the modules a device for measuring the filling level in the tank or possibly also in one of the modules. The nature and the positioning of the communications between the individual modules can be different, so that they are each adapted to the respective functions.